Midway Wolf Unit ‘Any U64’ CMOS Errors

Hacked program ROMs for each of the Wolf Unit games that allow game-swapping without the need for a game-specific security PIC have been freely available for a while (I won’t link them here but you might find them if you search for “Any U64”). However, depending on the PCB, conversions to 2 On 2 Open Ice Challenge and NBA (Maximum) Hangtime reportedly did not work correctly due to CMOS RAM issues:


Games such as Mortal Kombat 3 are fitted with an 8KB CMOS SRAM, such as an LH5268:

Note that the correct location of the CMOS RAM is U62, NOT U49

The NBA Hangtime games and Open Ice are fitted with a 32KB SRAM, such as an LH52B256L. These games store player records and thus require significantly more CMOS RAM.

In order to fully convert an Ultimate Mortal Kombat III to Open Ice, I had to perform the following modifications:

  1. Replace U62 with an LH52B256L.
  2. Add a zero ohm link to R644.
  3. Remove the 4.7K resistor at R138.


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